In my experience with web standards bodies, features useful to actual developers get denied and hand waved away with a grab bag of excuses (especially "security") up until the instant that one of the controlling corps smells money from one of the features.

At which point the feature will be fast tracked immediately, rammed through post haste, standards body be damned, all excuses evaporating overnight.

The main reason modern JS doesn't have threads is because Google controls Chrome, and they can multithread in there all they want; adding threads to JS will not help Google make more money.

Concurrency in JavaScript (2023) - https://www.honeybadger.io/blog/javascript-concurrency/

Modern JavaScript Concurrency (2025) - https://dev.to/gkoos/modern-javascript-concurrency-2025-edit...